Ink-jet printing apparatus, ink-jet printing method, and storage medium

ABSTRACT

In a print head, a plurality of ejection ports for ejecting metallic ink, including a solvent and particles for imparting a metallic gloss, are arranged in a predetermined direction. A plurality of printing scans are performed to the same area of the print medium to print an image on the print medium. In the printing scan, the metallic ink being ejected from the print head to a print medium while moving the print head in a scanning direction intersecting the predetermined direction. At least one of the plurality of printing scans is set as a first scan having a higher print ratio than the other printing scans.

The present application is a continuation of U.S. patent applicationSer. No. 16/027,836 filed Jul. 5, 2018, which claims the benefit under35 U.S.C. § 119 of Japanese Patent Application No. 2017-136434 filed onJul. 12, 2017, the entire contents of each of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an ink-jet printing apparatus thatejects a printing liquid, such as ink, from a print head to a printmedium while moving the print head to print an image. In particular, thepresent invention relates to an ink-jet printing apparatus, an ink-jetprinting method, and a storage medium which are used for ink-jetprinting using metallic ink with a function of imparting a metallicgloss.

Description of the Related Art

In recent years, metallic ink including metallic particles has beenprovided as ink that can be used to print on a print medium by, forexample, an ink-jet printing apparatus. The use of the metallic inkmakes it possible to impart a metallic gloss to a printed matter.

In the related art, a so-called one-pass printing method has been knownwhich ejects ink to the same area in one printing scan in order toimprove the gloss of an ink-jet printed matter. In general, in theone-pass printing method, unevenness is less likely to occur on thesurface of a printed matter than that in a so-called multi-pass printingmethod which can eject ink to the same area in a plurality of printingscans. As a result, a high gloss of the printed matter can be obtained.The gloss of the printed matter and a metallic gloss are different imagequality evaluation items. The metallic gloss is also improved by theone-pass printing method.

SUMMARY OF THE INVENTION

However, in the one-pass printing method, since printing is performed byone printing scan, a difference in the amount of ink ejected from eachnozzle of the ink-jet print head used and a difference (deviation) inlanding position appear as the density unevenness of a print image.

In contrast, in the multi-pass printing method, since a printing scan isperformed for the same area a plurality of times, the influence of adifference in the amount of ink ejected from each nozzle and thedeviation of the landing position of ink in an ejection direction isaveraged and the density unevenness of a print image is reduced.Although the surface irregularity of the print image increases, ametallic gloss is reduced.

Japanese Patent No. 5539118 discloses a method which performs a printingscan for ejecting clear ink (image quality improvement liquid) after aprinting scan for ejecting color ink to reduce gloss unevenness in anink-jet printing apparatus using the color ink and the clear ink. Asdescribed above, the gloss of a printed matter and the metallic glossare different image quality evaluation items. The ejection of the clearink makes it possible to improve the gloss of a general printed matter.However, the ejection of the clear ink is insufficient to improve themetallic gloss.

As such, in the method according to the related art, it is difficult tocreate a printed matter with a high metallic gloss and small densityunevenness.

The invention provides an ink-jet printing apparatus, an ink-jetprinting method, and a storage medium that can improve the metallicgloss of a printed matter and can reduce the density unevenness of theprinted matter in ink-jet printing using metallic ink with a function ofimparting a metallic gloss.

In the first aspect of the present invention, there is provided anink-jet printing apparatus comprising:

a print head in which a plurality of ejection ports for ejectingmetallic ink, including a solvent and particles for imparting a metallicgloss, are arranged in a predetermined direction; and

a control unit configured to perform a plurality of printing scans tothe same area of the print medium to print an image on the print medium,in the printing scan, the metallic ink being ejected from the print headto a print medium while moving the print head in a scanning directionintersecting the predetermined direction,

wherein the control unit sets at least one of the plurality of printingscans as a first scan having a higher print ratio than the otherprinting scans.

In the second aspect of the present invention, there is provided anink-jet printing method that uses a print head in which a plurality ofejection ports for ejecting metallic ink, including a solvent andparticles for imparting a metallic gloss, are arranged in apredetermined direction, a plurality of printing scans being performedto the same area of the print medium to print an image on the printmedium, in the printing scan, the metallic ink being ejected from theprint head to a print medium while moving the print head in a scanningdirection intersecting the predetermined direction, the methodcomprising:

a controlling step of performing the plurality of printing scans andsetting at least one of the plurality of printing scans as a first scanhaving a higher print ratio than the other printing scans.

In the third aspect of the present invention, there is provided anon-transitory computer-readable storage medium which stores a programcausing a computer to perform the ink-jet printing method according tothe second aspect of the present invention.

According to the invention, it is possible to create a printed matterwith a high metallic gloss and small density unevenness in ink-jetprinting using metallic ink including particles with a function ofimparting a metallic gloss.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an ink-jet printing apparatus accordingto an embodiment;

FIG. 2 is a diagram illustrating a print head according to theembodiment as viewed from an ejection port surface;

FIG. 3 is a block diagram schematically illustrating the configurationof a control system of the printing apparatus according to theembodiment;

FIG. 4 is a diagram illustrating an image data conversion processperformed by a control unit according to the embodiment;

FIG. 5 is a diagram illustrating a multi-pass print mode of the printingapparatus according to the embodiment;

FIG. 6 is a diagram illustrating an example of the formation state ofdots in a case where a plurality of silver ink droplets are ejected;

FIG. 7 is a diagram illustrating an example of the formation state ofdots in a case where a plurality of silver ink droplets are ejected;

FIG. 8 is a diagram illustrating an example of the formation state ofdots in a case where a plurality of silver ink droplets are ejected;

FIG. 9A is a diagram illustrating an example of masks for four passes inthe embodiment;

FIG. 9B is a diagram illustrating an example of a print data generationprocess;

FIG. 10 is a diagram illustrating an example of general masks for fourpasses;

FIG. 11 is a diagram schematically illustrating an example of an aspectin which a silver particle film is formed on a print medium in theembodiment;

FIG. 12A is a diagram illustrating an example of masks for four passesin the embodiment;

FIG. 12B is a diagram illustrating an example of a print data generationprocess;

FIG. 13A is a diagram illustrating an example of masks for four passesin the embodiment;

FIG. 13B is a diagram illustrating an example of a print data generationprocess;

FIG. 14 is a diagram schematically illustrating an example of an aspectin which a silver particle film is formed on a print medium in theembodiment;

FIG. 15A is a diagram illustrating an example of masks for four passesin the embodiment;

FIG. 15B is a diagram illustrating an example of a print data generationprocess;

FIG. 16A is a diagram illustrating an example of masks for four passesin the embodiment;

FIG. 16B is a diagram illustrating an example of a print data generationprocess;

FIG. 17A is a diagram illustrating an example of masks for four passesin the embodiment;

FIG. 17B is a diagram illustrating an example of a print data generationprocess;

FIG. 18A is a diagram illustrating an example of masks for two passes inthe embodiment;

FIG. 18B is a diagram illustrating an example of a print data generationprocess;

FIG. 19 is a diagram schematically illustrating an example of an aspectin which a silver particle film is formed on a print medium in theembodiment;

FIG. 20 is a diagram illustrating a process of quantizing multi-valueddata according to each pass ratio in the embodiment;

FIG. 21 is a flowchart illustrating a process of performing printingusing masks corresponding to a print duty in the embodiment;

FIG. 22A is a diagram illustrating original print data in theembodiment; and

FIG. 22B is a diagram illustrating an example of a print data generationprocess.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detailwith reference to the drawings.

<Printing Apparatus>

FIG. 1 is a side cross-sectional view illustrating the configuration ofa printing unit of an ink-jet printing apparatus 2 (hereinafter, simplyreferred to as a printing apparatus) that can be used in the invention.A carriage 1 including four print heads 5 and an optical sensor 32 canbe reciprocated in a X direction of FIG. 1 by the driving force of acarriage motor which is transmitted through a belt 34. The print heads 5eject ink in a Z direction on the basis of print data while the carriage1 is relatively moved in the X direction with respect to a print medium.In this way, an image corresponding to one printing scan is printed onthe print medium disposed on a platen 4. In a case where one printingscan ends, the print medium is transported in a Y direction (transportdirection) intersecting the X direction of FIG. 1 by a distancecorresponding to a print width in one printing scan. A plurality ofprinting scans and transport operations are alternately repeated tosequentially form an image on the print medium.

The optical sensor 32 performs a detection operation while being movedtogether with the carriage 1 to determine whether a print medium ispresent on the platen 4. A recovery unit 30 for performing a maintenanceprocess for the print heads 5 is provided at a position that is locatedin a scanning area of the carriage 1 and is outside the platen 4.

<Print Head>

FIG. 2 is a diagram illustrating the print heads 5 provided in thecarriage 1 as viewed from an ejection port surface (that is, from adirection opposite to the Z direction in FIG. 1). Each of the printheads 5 includes one of ejection port arrays 101 to 104 which arearranged in parallel in the X direction. In each of the ejection portarrays 101 to 104, a plurality of (here, n=32) ejection ports forejecting ink as liquid droplets are arranged in a predetermineddirection (the Y direction in FIG. 2; also referred to as an arrangementdirection) at a pitch of 1200 dpi. Metallic (Me), cyan (C), magenta (M),and yellow (Y) inks are ejected from the ejection port arrays 101 to104, respectively.

In this embodiment, the print heads 5 are provided for each ink color.However, the invention is not limited thereto. One print head may have aplurality of ejection port arrays that can eject a plurality of colorinks.

<Control Unit>

FIG. 3 is a block diagram schematically illustrating the configurationof a control system (print control device) of the ink-jet printingapparatus 2. A main control unit 300 includes, for example, a CPU 301that performs processing operations, such as calculation, selection,determination, and control, a ROM 302 that stores a control program tobe executed by the CPU 301, a RAM 303 that is used as a print databuffer, and an input/output port 304. A driving circuit 305 thatcontrols an LF motor 309 for transporting the print medium, a drivingcircuit 306 that controls a CR motor 310 for reciprocating the carriage1, and a driving circuit 307 that drive (perform ejection control for)each print head 5 are connected to the input/output port 304. Inaddition, the main control unit 300 is connected to a host computer 312through an interface circuit 311. The following characteristic controlprocess of the invention is performed by a printer driver installed inthe host computer 312 or is performed by the CPU 301 of the printingapparatus 2 according to the program or various parameters stored in theROM 302.

<Print Data Generation Process>

FIG. 4 is a diagram illustrating an image data conversion processperformed by the host computer 312 and the printing apparatus 2.Original image data 401 is 600-dpi RGB data. First, the printer driverconverts the image data 401 into 600-dpi density data 402 correspondingto ink colors CMYMe used by the printing apparatus 2. Then, the printerdriver performs data processing according to a multi-valued errordiffusion method or a dither method to convert the CMYMe density data402 into quantization data 403 with three levels (gradation values) of 0to 2. Here, for example, data is quantized into three values. However,the quantization value N is not limited thereto. The host computer 312transmits quantization data of each ink color to the printing apparatus2.

In a case where the CPU 301 received ternary image data, the CPU 301converts the 600-dpi quantization data 403 into 1200-dpi binary printdata 404 with reference to a dot arrangement pattern that is stored inthe ROM 302 in advance. In addition, the CPU 301 stores the print datain a print buffer prepared in the RAM 303. The print data is binary datathat determines printing “1” or non-printing “0” for each of 2×2 pixelsarranged at a pitch of 1200 dpi.

In a case where the print data corresponding to one or more printingscans is stored in the RAM 303, the CPU 301 performs a printingoperation based on the print data 404 according to the program stored inthe ROM 302. Specifically, the CPU 301 directs the print heads 5 toperform an ejection operation while reading the binary print data 404corresponding to each printing scan. At that time, a print resolution inthe main scanning direction may be 1200 dpi or 600 dpi. In a case wherethe print resolution is 600 dpi, as illustrated in a print result 405,dots corresponding to print data 1 and 2 which are arranged in the mainscanning direction are printed so as to overlap each other at a pixelposition A. In addition, dots corresponding to print data 3 and 4 areprinted so as to overlap each other at a pixel position B. The CPU 301directs the print heads 5 to perform an ejection operation on the basisof the print data 404 while controlling various motors through theinput/output port 304 as needed. In this way, an image corresponding toone page is printed on the print medium.

<Multi-Pass Printing>

Next, multi-pass printing performed by the printing apparatus accordingto this embodiment will be described. The multi-pass printing is aprinting method in which a printing scan is performed in the same unitarea (hereinafter, also referred to as the same area) of the printmedium a plurality of times to print an image.

FIG. 5 is a diagram illustrating a mode in which the multi-pass printingis performed by four printing scans using a pass mask among the printmodes performed by the printing apparatus according to this embodiment.FIG. 5 schematically illustrates, for example, the print head, a maskpattern of the pass mask, and a printed dot pattern in a case where animage is completely printed in the same area by four printing scans.

In FIG. 5, reference symbol P0001 indicates the print head. Here, forsimplicity of illustration and description, the print head having 16ejection ports (hereinafter, also referred to as nozzles) isillustrated. As illustrated in FIG. 5, a nozzle array is divided intofour nozzles groups, that is, first to fourth nozzle groups, each ofwhich includes four nozzles, and is used. Reference symbol P0002indicates the mask pattern of the pass mask and a mask pixel(hereinafter, also referred to as a printing allowance pixel) thatallows the printing of a pixel corresponding to each nozzle isillustrated in black. The mask patterns corresponding to the four nozzlegroups complement each other. In a case where the four patterns overlapeach other, all of 4×4 pixels become the printing allowance pixels. Thatis, the printing of an area of 4×4 pixels is completed by four patterns.

Reference symbol P0003 to P0006 indicate the formed dot arrangementpatterns and indicate an aspect in which the printing scan is repeatedto form an image. As illustrated in the patterns, in the multi-passprinting, dots are formed on the basis of the binary print data (dotdata) generated by the mask patterns corresponding to each nozzle groupin each printing scan. Then, whenever the printing scan ends, the printmedium is transported in an arrow direction in FIG. 5 by a distancecorresponding to the width of the nozzle group. As such, the printing ofan image in the area corresponding to the width of each nozzle group onthe print medium is completed by four printing scans.

<Metallic Ink>

(Metallic Particle)

The metallic ink used in this embodiment includes metallic particles.The content (mass %) of the metallic particles in the ink is preferablyequal to or greater than 0.1 mass % and equal to or less than 30.0 mass% and more preferably equal to or greater than 1.0 mass % and equal toor less than 15.0 mass % with respect to the total mass of the ink.

The metallic particle is not particularly limited. Examples of themetallic particle include gold, silver, copper, platinum, aluminum,titanium, chromium, iron, nickel, zinc, zirconium, and tin particles.The metallic particles may be single metal particles, alloy particles,or a combination thereof. The metallic particles are preferably gold,silver, or copper particles and more preferably silver particles interms of the preservation stability of the metallic particles and thegloss of a formed image. The silver particles improve the gloss of theformed image and are achromatic. Therefore, the silver particles areparticularly superior in reproducing a metallic color in a wide range ina case where the silver particles are combined with a colored ink.

The average particle diameter of the silver particles used in thisembodiment is preferably equal to or greater than 1 nm and equal to orless than 200 nm and more preferably equal to or greater than 10 nm andequal to or less than 100 nm in terms of the preservation stability ofink and the gloss of an image formed by the silver particles.

(Other Components)

The metallic ink used in this embodiment may include water as a solvent(ion-exchanged water) and various additives, such as a surfactant, awater-soluble organic solvent, a pH adjustment agent, an antirust agent,an antiseptic agent, a mildew proofing agent, an antioxidant, areduction inhibitor, and an evaporation accelerator, in addition to theabove-mentioned metallic particles.

Next, the formation state of dots on a print medium by the metallic inkwhich is one of the characteristics of the invention and the formationof a film by the metallic particles in the metallic ink will bedescribed.

In the following embodiments, silver nano-ink (hereinafter, alsoreferred to as “silver ink”) including silver particles with anano-order particle size which are dispersed in a solvent is given as anexample of the metallic ink used.

FIG. 6 is a diagram schematically illustrating the formation states ofdots in a case where a plurality of silver ink droplets are ejected to aprint medium.

FIG. 6 is a diagram illustrating a case in which, after a first inkdroplet is ejected, a second ink droplet is ejected, as viewed from thecross-sectional direction of the print medium.

A part (a) of FIG. 6 illustrates a first ink droplet 604 ejected from anozzle and a second ink droplet 605 ejected a predetermined time afterthe ejection of the first ink droplet 604, immediately before the inkdroplets land on a print medium 601. Each of the ink droplets includessilver particles 602 and a solvent 603. In a state where the silverparticles with a nano-order size are dispersed in the solvent, thesilver particle does not look achromatic silver due to a plasmon effect.

Then, the first ink droplet 604 lands on the print medium 601 before thesecond ink droplet 605 lands (part (b) of FIG. 6). The solvent 603 inthe first ink droplet 604 that lands first is infiltrated into the printmedium, or is evaporated from the surfaces of the ink droplet, so thatthe amount of solvent is reduced. Accordingly, the silver particles 602in the first ink droplet 604 come into contact with each other and thediameter of the silver particle increases or the shape of the silverparticle changes. As a result, a silver particle film in which thesilver particles are densely concentrated is formed in the vicinity ofthe surface of the print medium and the plasmon effect does not occur.Therefore, a silver color which is an achromatic color is exhibited(part (c) of FIG. 6).

In a case where the subsequent second ink droplet 605 lands in thevicinity of the first ink droplet 604 while the silver particle film isbeing formed by the previous first ink droplet 604, a silver particlefilm is formed with the infiltration or evaporation of the solvent inthe second ink droplet 605 (part (c) of FIG. 6). At that time, in a casewhere the first ink droplet 604 that is forming the silver particle filmand the second ink droplet 605 come into contact with each other, theink droplets are easily combined to form a silver particle film 606(part (d) of FIG. 6).

FIG. 7 is a diagram illustrating a case in which a second ink droplet isejected after an elapse of certain time after a first ink droplet isejected.

A part of FIG. 7 illustrates a first ink droplet 704 ejected from thenozzle and a part (b) of FIG. 7 illustrates a state in which a secondink droplet 705 is ejected after a predetermined time that is longerthan that in the case illustrated in the part (a) of FIG. 6. Each of theink droplets 704 and 705 includes silver particles 702 and a solvent703, similarly to the case illustrated in FIG. 6. The first ink droplet704 lands on a print medium 701 before the second ink droplet 705 lands(part (b) of FIG. 7). As illustrated in a part (c) of FIG. 7, in thefirst ink droplet 704 that lands first, the solvent is infiltrated orevaporated and the amount of solvent is reduced. With the reduction inthe amount of solvent, the silver particles 702 form a silver particlefilm in the vicinity of the surface of the print medium, similarly tothe case illustrated in FIG. 6. However, in a state where ink is ejectedas illustrated in FIG. 7, after the previous ink droplet 704 forms asilver particle film in a dot shape, the subsequent second ink droplet705 lands on the print medium (part (d) of FIG. 7). Therefore, thecontact and combination of the ink droplets while dots are being formedas described in FIG. 6 do not occur and the first ink droplet 704 andthe second ink droplet 705 individually form a silver particle film 706.In this case, since the second ink droplet 705 forms a silver particlefilm on the first ink droplet 704 in a portion in which the first inkdroplet 704 and the second ink droplet 705 overlap each other, theunevenness of the surface is large (part (e) of FIG. 7).

As such, in the silver particle film formed on the print medium by thesilver ink droplets, the unevenness of the surface varies depending onthe magnitude (length) of a difference in landing time between aplurality of silver ink droplets. In a case where the difference inlanding time is small (short), a smooth film with small surfaceunevenness is formed. Therefore, a metallic gloss is high. In a casewhere the difference in landing time is large (long), the unevenness ofthe surface is large and smoothness is low. Therefore, a metallic glossis low.

In addition, the metallic gloss varies depending on the amount of silverink droplets that are ejected at a time. Next, a difference in metallicgloss depending on the amount of ink ejected will be described.

FIG. 8 is a diagrams schematically illustrating the formation state ofdots in a case where a large number of silver ink droplets are ejectedto a print medium at a time.

A part (a) of FIG. 8 illustrates first to fifth ink droplets 804 to 808ejected from the nozzles before they land on a print medium 801.Similarly to FIG. 6, each ink droplet includes silver particles 802 anda solvent 803. In the example illustrated in FIG. 8, the amount of inkejected is more than that in FIG. 6, a difference in the landing timebetween the ink droplets is less than that in FIG. 6, and the first tothird ink droplets 804 to 806 land on the print medium 801 before thefourth ink droplet 807 and the fifth ink droplet 808 land (part (b) ofFIG. 8). As illustrated in a part (b) of FIG. 8, in the first to thirdink droplets 804 to 806 that land first, the silver particles start tocome into contact with each other immediately after the first to thirdink droplets land and a silver particle film is formed in the vicinityof the surface of the print medium with the infiltration or evaporationof the solvent, similarly to FIG. 6. Then, in a case where the fourthink droplet 807 and the fifth ink droplet 808 land on the previous inkdroplets, in the fourth ink droplet 807 and the fifth ink droplet 808,with the infiltration or evaporation of the solvent, the silverparticles start to come into contact with each other and a silverparticle film starts to be formed (part (c) of FIG. 8).

In this case, while the infiltration or evaporation of the solvents inthe first to third ink droplets 804 to 806 has not yet ended, all of theink droplets come into contact with each other. A large number of silverparticle films are formed for a time that is longer than that in FIG. 6and FIG. 7. Therefore, a silver particle film 809 that has small surfaceunevenness, is smooth, and has a high metallic gloss is formed (part (d)of FIG. 8).

The time (speed) required for a predetermined amount of solvent to beinfiltrated into the print medium or to be evaporated is the same.Therefore, in a case where a large number of silver ink droplets areejected at a time, the amount of ink per unit area increases and thetime required for the solvent to be infiltrated and evaporatedincreases. In addition, since it takes a lot of time for the silverparticles to be fixed on the print medium, the time for obtaining anopportunity at which the silver particles to come into contact with eachother is long. As a result, a metal film is formed for a long time andthe number of silver particles that contribute to producing a silvercolor increases. Therefore, a metallic gloss is improved.

As such, in a case where a printed matter is created by ejecting aplurality of silver ink droplets to form a silver particle film on theprint medium using an ink-jet printing method, it is preferable that aprint ratio is set to a high value in one printing scan to eject a largenumber of silver ink droplets in order to improve the production of asilver color and metallic gloss. In other words, in a case where asilver ink is used, it is effective to eject ink using a printing scanin which a high print ratio that is not set in normal color ink or clearink is set, in order to produce a silver color. For example, in a casewhere the print ratio of a specific pass is set to a significantly highvalue in a printing method using normal color ink and clear ink as inJapanese Patent No. 5539118, image deterioration, such as densityunevenness or bleeding, is likely to occur in a color image. Incontrast, in a case where printing is performed using the silver inkaccording to this embodiment, the image deterioration does not occureven if the print ratio of a specific pass is set to a significantlyhigh value.

By the way, in a print head of an ink-jet printing apparatus including aplurality of nozzles, there is a difference in the amount of ink ejectedfrom each nozzle and a difference (deviation) in the landing position ofan ink droplet due to a manufacturing tolerance. The difference in theamount of ink ejected and the deviation of the landing position of theink droplet in the ejection direction cause the deterioration of imagequality. It is preferable to use multi-pass printing in order to preventthe deterioration of image quality as described above. That is, in themulti-pass printing, a plurality of printing scans are performed toprint an image in the same unit area. Therefore, the influence of thedifference in the amount of ink ejected from each nozzle and thedeviation is averaged and the density unevenness of a print image isreduced.

In this embodiment, among a plurality of passes in the multi-passprinting, a printing pass (first scan) with a function of improving theproduction of a silver color and a metallic gloss and a printing pass(second scan) with a function of reducing density unevenness caused by avariation in the manufacture of nozzles of the print head are set. Amethod for setting the print ratios of these passes (first and secondscans) and a printing order will be described in detail with referenceto specific examples.

Printing by the printing apparatus according to this embodiment isachieved by the print data generation method illustrated in FIG. 4.

First Embodiment

In a first embodiment of the invention, the number of passes inmulti-pass printing using silver ink including silver particles is 4. Inparticular, the print ratio of a fourth pass is set to a high value.

A characteristic mask pattern used in this embodiment will be describedwith reference to FIGS. 9A and 9B. FIG. 9A illustrates mask patterns901, 902, 903, and 904 for the first to fourth passes as mask patternsfor four passes. The printing allowance pixel, that is, the pixel towhich ink is ejected is a black pixel.

FIG. 10 illustrates mask patterns 1001, 1002, 1003, and 1004 for thefirst to fourth passes as general mask patterns for four passes.

The mask patterns according to this embodiment illustrated in FIG. 9Aare different from the general mask patterns illustrated in FIG. 10 inthe following points. That is, in the first to third passes of the maskpatterns according to this embodiment, the printing allowance pixels aretwo pixels among all of the print pixels (16 pixels) and the print ratiois set to a low value of 12.5%. In the fourth pass, the printingallowance pixels are 10 pixels and the print ratio is set to a highvalue of 62.5%. That is, the print ratios of all of the four passes area plurality of types and are not uniform. In addition, in thisembodiment, the print ratio of one pass among the four passes is set tobe higher than that of the other passes.

Hereinafter, among a plurality of passes (printing scans), a pass havinga higher print ratio than the other passes is referred to a “pass(printing scan) with a high print ratio” or a “first scan”. In such afirst scan, one printing scan or a plurality of printing scans may beincluded. In a case where the first scan includes a plurality ofprinting scans, the print ratios of the printing scans may be equal toeach other or may be different from each other. In addition, a pass witha print ratio (a relatively low print ratio) that is different from thatof the first scan is referred to as a “pass (printing scan) with a lowprint ratio” or a “second scan”.

In the general mask patterns illustrated in FIG. 10, the printingallowance pixels in each pass are four pixels and the print ratios areequally set to 25%. In this embodiment, the mask pattern illustrated inFIG. 9A is used as a mask pattern for silver ink (Me) and the generalmask patterns illustrated in FIG. 10 are used as mask patterns for theother color inks (CMY).

A method for calculating the print ratio of the fourth pass (the passwith a high print ratio (first pass)) in the mask patterns illustratedin FIG. 9A will be described below. A reference print ratio iscalculated from a dot size (an area covered by a dot) that is formed ona print medium by one ink droplet and a unit area on the print medium.In this embodiment, the diameter of a dot formed by one silver inkdroplet is 61.0 μm, that is, the radius of the dot is 30.5 μm. Inaddition, the unit area of a 600-dpi (42.3 μm) unit grid on the printmedium is about 1789.3 μm². A minimum print ratio (target print ratio) krequired to cover the total area (unit area) of the unit grid with dotscan be calculated by the following Expression (1):k=1789.3/(30.5×30.5×3.14)=0.613  Expression (1)

The print ratio of the pass (first scan) with a high print ratio is setto be equal to or greater than a target print ratio k of 61.3%. In thiscase, even if ink droplets are simultaneously ejected in the first scanso as to dispersively form dots on the print medium, the ink dropletscertainly come into contact with each other. For this reason, in thisembodiment, the print ratio of the pass with a high print ratio is setto 62.5% that is higher than the target print ratio k (61.3%). Inaddition, for the print ratios of the first to third passes (secondscan) with a low print ratio, the remainder of 37.5% is equally divided.Each of the print ratios of the first to third passes is set to 12.5%.

The mask patterns illustrated in FIG. 9A to which the print ratios havebeen set as described above are applied as the mask patterns for silverink.

FIG. 9B is a diagram illustrating a process for generating the printdata of each pass from the print data generated by the print datageneration process flow illustrated in FIG. 4, using the mask patternsillustrated in FIG. 9A.

FIG. 9B illustrates print data 1101 for silver ink obtained bybinarizing a so-called solid image in which dots are formed on all printpixels. A masking process is performed for the print data 1101 using themask patterns 901 to 904 illustrated in FIG. 9A to generate print data1102, 1103, 1104, and 1105 of each pass. Since the print data 1101 isused for a solid image, the print data of each pass corresponds to themask patterns illustrated in FIG. 9A.

Next, an aspect in which the print head sequentially ejects silver inkdroplets corresponding to the print data of each pass to apply silverink to a print medium will be described.

FIG. 11 including parts (a) to (0 is a diagram schematicallyillustrating an aspect in which a silver particle film is formed on aprint medium in a case where the print head ejects silver ink dropletson the basis of the print data of each pass illustrated in FIG. 9B. Thesilver ink ejected in each pass forms a silver particle film on theprint medium according to the amount of ink ejected and the differencein landing time, as described with reference to FIGS. 6 to 8.

As the time for contact silver particles with each other becomes longer,that is, the time until the infiltration of a solvent in ink into theprint medium or the evaporation of the solvent ends becomes longer, ametal film formed by the silver particles has higher density. Therefore,a silver particle film with a high metallic gloss is formed.

The parts (a) to (d) of FIG. 11 illustrate a state immediately beforethe silver ink ejected from the print head in each pass lands on a printmedium 1201. The time difference between the passes is about 300 msec.The time from the landing of ink-jet ink including the silver ink usedin this embodiment on a print medium to the end of the infiltration of asolvent in the ink into the print medium is about several tens ofmilliseconds per droplet. As illustrated in the parts (a) to (c) of FIG.11, since the number of ink droplets ejected (applied) in each of thefirst to third passes is small, the infiltration of ink ejected in theprevious pass into the print medium almost ends before ink is ejected inthe subsequent pass. Similarly, as illustrated in the part (d) of FIG.11, before ink is ejected in the fourth pass, the infiltration of theink droplets ejected up to the third pass into the print medium almostends. Since the number of ink droplets ejected in the fourth pass islarge, the infiltration of the solvent in the ink droplets into theprint medium starts in a state where the ink droplets come into contactwith each other, as illustrated in the part (e) of FIG. 11. In thefourth pass, since the amount of ink ejected is large, the time untilthe infiltration or the solvent into the print medium or the evaporationof the solvent ends is long. Therefore, the formation of a metal film bythe silver particles progresses and a silver particle film with a highmetallic gloss is formed (part (f) of FIG. 11).

The influence of a difference in the amount of ink ejected from eachnozzle and the deviation of the landing position of the ink in theejection direction is averaged by the multi-pass printing and thedensity unevenness of a print image is reduced. Since the contact timeof the silver particles in the fourth pass is maintained for a longtime, the formation of a metal film by the silver particles progressesand an image with a high metallic gloss is printed. As such, in thisembodiment, it is possible to print an image with a high metallic glossand small density unevenness.

In this embodiment, the pass (first scan) with a high print ratioillustrated in the part (d) of FIG. 11 is set to print an image with ahigh metallic gloss. The print ratio of the pass with a high print ratiois not limited to the print ratio set in this embodiment. As describedabove, it is important to increase the number of ink droplets that comeinto contact with each other at the same time in order to increase ametallic gloss. Therefore, it is effective to increase the print ratioof the first scan. It is not preferable that the print ratio of thefirst scan is too low. The print ratio of the first scan may be a valueat which a silver particle film with an allowable metallic gloss levelcan be formed. It is preferable that the print ratio for bringing alarge number of ink droplets into contact with each other at the sametime is set to a value that is equal to or greater than half the sum(total print ratio) of the print ratios of each pass such that anallowable metallic gloss level is obtained.

In this embodiment, the pass with a high print ratio among four passesis the fourth pass. However, the pass with a high print ratio is notlimited to the fourth pass. The pass with a high print ratio may be setto any one of the first to third passes. In this case, similarly, thecontact time of the silver particles increases and the formation of ametal film by the silver particles progresses to increase a metallicgloss. In a case where the pass with a high print ratio is set to anyone of the first to third passes, a metallic gloss is slightly lowerthan that in case where the pass with a high print ratio is set to thefourth pass, but it is possible to obtain a sufficiently allowablemetallic gloss. Therefore, it is possible to change the order of thepasses including the pass with a high print ratio.

In this embodiment, for the passes (second scans) other than the pass(first scan) with a high print ratio, the total print ratio of thepasses other than the pass with a high print ratio is equally divided.For the second scans, different print ratios may be set. Since thesecond scan has a function of reducing density unevenness, it ispreferable to set the print ratio capable of reducing densityunevenness. In some case, the print ratio may be set to 0% at which noink is ejected. However, in a case where all of the print ratios of thesecond scans are set to 0%, printing is substantially the same asone-pass printing and the function of reducing density unevenness is notachieved, which is not preferable. In addition, it is not preferablethat the print ratios of the second scans are close to 0% without limitfor the same reason. Therefore, it is preferable that the second scanwith the function of reducing density unevenness is performed at leastone time among all of the printing scans and the print ratios of thesecond scans are at least one type. In addition, it is preferable thatthe sum of the print ratios of the second scans with the function ofreducing density unevenness is set to a ratio that is less than half thetotal print ratio. That is, it is preferable that the sum of the printratios of the second scans is not greater than the sum of the printratios of the first scans. For the print ratios of the second scans, thedifference between the print ratios of each pass and a difference ineffect will be described in the following other embodiments.

In the multi-pass printing, the number of passes is not limited to fourand may be appropriately changed. In addition, the pass (first scan)with a high print ratio is not limited to one (one pass) of the passes.The print ratios of two or more passes may be set to a high value.

The configuration in which the print ratios of a plurality of passes areset to a high value can be applied as long as a sufficiently allowablemetallic gloss is obtained even if a metallic gloss is less than that ina case where one pass (first scan) has a high print ratio. In this case,the sum of the print ratios of a plurality of first scans is preferablyset so as to be equal to or greater than the print ratio in a case wherethe first scan is performed once, that is, the print ratio calculated bythe above-mentioned Expression (1). In this case, it is preferable thateach of the print ratios of the plurality of first scans is greater thana value in a case where the print ratios of all passes are equal to eachother. The reason is as follows. In a case where each of the printratios of the plurality of first scans is equal to the value in a casewhere the print ratios of all passes are equal to each other, the amountof ink ejected per pass is small and the contact between the inkdroplets is reduced. As a result, a silver particle film with a lowmetallic gloss is formed.

It is preferable that two or more passes as the passes (first scans)with a high print ratio are successive in order to accelerate thecontact between the ink droplets and the formation of a silver particlefilm.

As such, in a case where two or more first scans are set, it ispreferable that the print ratio of the first scan is greater than avalue in a case where all of the passes have the same print ratio. Inaddition, it is more preferable that the sum of the print ratios of aplurality of first scans is equal to or greater than the print ratio ina case where the number of first scans is one. It is preferable that twoor more first scans are successively performed.

In this embodiment, a case where the original multi-valued data isprocessed into binary data and then print data applied to each passusing the mask patterns is generated has been described. However, othermethods can be used as the method for generating the print data of eachpass. For example, a method may be applied which generates themulti-valued data of each process from the original multi-valued dataand binarizes the multi-valued data of each pass to generate print data.In addition, the print medium used is not particularly limited. Anyprint medium can be used as long as a silver particle film is formed onthe print medium by the silver ink used and a sufficiently high metallicgloss is obtained.

Second Embodiment

In a second embodiment, similarly to the first embodiment, the number ofpasses in multi-pass printing is four and the print ratio of the fourthpass is set to be higher than that in the first embodiment.

FIG. 12A illustrates mask patterns 1301, 1302, 1303, and 1304 for firstto fourth passes as mask patterns for four passes. A black pixel is theprinting allowance pixel.

In the mask patterns 1301, 1302, and 1303 for the first to third passes,the printing allowance pixel is one pixel among all print pixels (16pixels) and the print ratio is set to 6.25% that is less than that inthe first embodiment. In the mask pattern 1304 for the fourth pass, theprinting allowance pixels are 13 pixels and the print ratio is set to81.25% that is higher than that in the first embodiment.

FIG. 12B is a diagram illustrating a process for generating the printdata of each pass from the print data generated by the same method asthat in the first embodiment, using the mask patterns illustrated inFIG. 12A.

FIG. 12B illustrates print data 1401 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 1401 using the maskpatterns 1301 to 1304 illustrated in FIG. 12A to generate print data1402, 1403, 1404, and 1405 of each pass. This embodiment is the same asthe first embodiment except that the print ratio of each pass isdifferent from that in the first embodiment.

For ink droplets ejected in the first to third passes, the influence ofa difference in the amount of ink ejected from each nozzle and thedeviation of the landing position of ink in the ejection direction isaveraged by the effect of the multi-pass printing and the densityunevenness of a print image is reduced. Since the contact time of thesilver particles in the fourth pass is maintained for a long time, theformation of a metal film by the silver particles progresses and ametallic gloss is improved. In particular, since the print ratio of thefourth pass is higher than that in the first embodiment, the effect ofreducing density unevenness is slightly reduced, but a metallic glosscan be higher than that in the first embodiment. In this embodiment, itis possible to print an image with a high metallic gloss and smalldensity unevenness.

Third Embodiment

In a third embodiment, similarly to the first embodiment, the number ofpasses in multi-pass printing is four, the print ratio of the first passis set to a high value, and the print ratios of the second to fourthpasses are set to a lower value.

FIG. 13A illustrates mask patterns 1501, 1502, 1503, and 1504 for firstto fourth passes as mask patterns for four passes. A black pixel is theprinting allowance pixel. In the mask pattern 1501 for the first pass,the printing allowance pixels are 10 pixels among all print pixels (16pixels) and the print ratio is set to a high value of 62.5%. In the maskpatterns for the second to fourth passes, the printing allowance pixelsare two pixels and the print ratio is set to a low value of 12.5%.

FIG. 13B illustrates print data 1601 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 1601 using the maskpatterns 1501 to 1504 illustrated in FIG. 13A to generate print data1602, 1603, 1604, and 1605 of each pass.

Parts (a) to (f) of FIG. 14 are diagrams illustrating an aspect in whicha print head ejects silver ink on the basis of the print data of eachpass illustrated in FIG. 13B to form a silver particle film on a printmedium 1701. The pars (a) to (d) of FIG. 14 illustrate a stateimmediately before the silver ink ejected from the print head in eachpass lands on the print medium 1701. Similarly to the first embodiment,the time difference between the passes is about 300 msec and the timefrom the landing of the silver ink on the print medium to the end ofinfiltration of a solvent in the ink into the print medium is aboutseveral tens of milliseconds per droplet.

As illustrated in the part (a) of FIG. 14, a large number of inkdroplets are ejected (supplied) in the first pass. Therefore, in a casewhere the ink droplets land on the print medium 1701, the ink dropletscome into contact with each other and the infiltration of a solvent inthe ink into the print medium starts as illustrated in the part (b) ofFIG. 14. As illustrated in the part (b) of FIG. 14, a small number ofink droplets are ejected in the second pass. However, the infiltrationof the solvent in the ink ejected in the first pass into the printmedium has not yet ended, all of the ink droplets come into contact witheach other, and the solvent remains on the print medium. Therefore, theink droplets ejected in the second pass, which have come into contactwith the ink droplets ejected in the first pass, start to be infiltratedand the formation of a metal film by some silver particles progresses.

As illustrated in the parts (c) and (d) of FIG. 14, before ink dropletsare ejected in the third and fourth passes, the infiltration of the inkejected in the previous passes into the print medium almost ends. Sincethe number of ink droplets ejected in the third and fourth passes issmall, these ink droplets do not come into contact with each other andthe infiltration of the solvent in the ink into the print medium starts.As a result, the shape of dots corresponding to the ink droplets whichhave been ejected in the third and fourth passes remains (part (e) ofFIG. 14). Then, a silver particle film is formed by, for example, theevaporation of the solvent in the ink a d the like (part (f) of FIG.14).

Since the contact time of the silver particles in the first pass ismaintained for a long time, the formation of a metal film by the silverparticles progresses and a high metallic gloss is obtained. In addition,for the ink droplets ejected in the second to fourth passes, theinfluence of a difference in the amount of ink ejected from each nozzleand the deviation of the landing position of ink in the ejectiondirection is averaged by the effect of the multi-pass printing and animage with small density unevenness is printed. Since a metal film isformed by the ink droplets ejected in the second to fourth passes in astate where the shape of dots remains, a metallic gloss is slightlylower than that in the first embodiment, but an image whose densityunevenness has been significantly reduced is printed. In thisembodiment, it is possible to print an image with a sufficiently highmetallic gloss and small density unevenness.

The comparison between the first embodiment and the third embodimentshows that the execution of the first scan with a high print ratio inthe second half of a plurality of printing scans rather than in thefirst half is also effective in improving a metallic gloss.

Fourth Embodiment

In a fourth embodiment, the number of passes in multi-pass printing isfour similarly to the first embodiment and the print ratios of the firstto third passes are set to different values unlike the first embodiment.

FIG. 15A illustrates mask patterns 1801, 1802, 1803, and 1804 for firstto fourth passes as mask patterns for four passes. A black pixel is theprinting allowance pixel. In the mask pattern 1801 for the first pass,the printing allowance pixels are three pixels among all print pixels(16 pixels) and the print ratio is 18.75%. In the mask pattern 1802 forthe second pass, the printing allowance pixels are two pixels and theprint ratio is 12.5%. In the mask pattern 1803 for the third pass, theprinting allowance pixel is one pixel and the print ratio is 6.25%. Inthe mask pattern 1804 for the fourth pass, the printing allowance pixelsare 10 pixels and the print ratio is 62.5%.

FIG. 15B illustrates print data 1901 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 1901 using the maskpatterns 1801 to 1804 illustrated in FIG. 15A to generate print data1902, 1903, 1904, and 1905 of each pass. This embodiment is the same asthe first embodiment except that the print ratios of the first to thirdpasses are different from those in the first embodiment.

For ink droplets ejected in the first to third passes, the influence ofa difference in the amount of ink ejected from each nozzle and thedeviation of the landing position of ink in the ejection direction isaveraged by the effect of the multi-pass printing and the densityunevenness of a print image is reduced. Since the contact time of thesilver particles in the fourth pass is maintained for a long time, theformation of a metal film by the silver particles progresses and ametallic gloss is improved.

Since the print ratios of the first to third passes are different fromthose in the first embodiment, there is a difference in the effect ofreducing density unevenness. In particular, since the print ratio of thethird pass is lower than those of the first pass and the second pass,the infiltration of the ink droplets ejected (applied) in the third passinto the print medium is completed in a short time. Therefore, theinfiltration of the solvent in the ink droplets ejected up to the thirdpass into the print medium is completed before the ink droplets areejected in the fourth pass. Since the number of ink droplets ejected inthe fourth pass is large, the time until the solvent in the ink dropletsis infiltrated into the print medium or the solvent is evaporated islong as in the first embodiment. Therefore, the formation of a metalfilm by the silver particles progresses and a silver particle film witha high metallic gloss is formed. The function of each pass is moreeffective than that in the first embodiment. As a result, it is possibleto print an image with a high metallic gloss and low density unevenness.

Fifth Embodiment

In a fifth embodiment, the number of passes in multi-pass printing isfour similarly to the first embodiment and the first to third passesinclude a pass in which no ink is ejected, that is, a pass with a printratio of 0%.

FIG. 16A illustrates mask patterns 2001, 2002, 2003, and 2004 for firstto fourth passes as mask patterns for four passes. A black pixel is theprinting allowance pixel. In the mask pattern 2001 for the first pass,the number of printing allowance pixels among all print pixels (16pixels) is 0 and the print ratio is 0%. In each of the mask patterns2002 and 2003 for the second and third passes, the printing allowancepixels are three pixels and the print ratio is 18.75%. In the maskpattern 2004 for the fourth pass, the printing allowance pixels are 10pixels and the print ratio is set to a high value of 62.5%.

FIG. 16B illustrates print data 2101 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 2101 using the maskpatterns 2001 to 2004 illustrated in FIG. 16A to generate print data2102, 2103, 2104, and 2105 of each pass. This embodiment is the same asthe fourth embodiment except that the print ratios of the first to thirdpasses are different from those in the fourth embodiment.

For ink droplets ejected (applied) in the second and third passes, theinfluence of a difference in the amount of ink ejected from each nozzleand the deviation of the landing position of ink in the ejectiondirection is averaged by the effect of the multi-pass printing and thedensity unevenness of a print image is reduced. Since the contact timeof the silver particles in the fourth pass is maintained for a longtime, the formation of a metal film by the silver particles progressesand a metallic gloss is improved. Since no ink droplets are ejected inthe first pass, the effect of reducing density unevenness is slightlyless than that in the fourth embodiment. However, in this embodiment, itis also possible to print an image with a sufficiently high metallicgloss and small density unevenness.

Sixth Embodiment

In a sixth embodiment, the number of passes in multi-pass printing isfour similarly to the first embodiment, the print ratios of the firstand second passes are set to a low value, and the print ratios of thethird and fourth passes are set to a high value.

FIG. 17A illustrates mask patterns 2201, 2202, 2203, and 2204 for firstto fourth passes as mask patterns for four passes. A black pixel is theprinting allowance pixel. In the mask patterns 2201 and 2202 for thefirst and second passes, the printing allowance pixels are two pixelsamong all print pixels (16 pixels) and the print ratio is set to a lowvalue of 12.5%. In the mask patterns 2203 and 2204 for the third andfourth passes, the printing allowance pixels are six pixels and theprint ratio is set to a high value of 31.25%.

FIG. 17B illustrates print data 2301 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 2301 using the maskpatterns 2201 to 2204 illustrated in FIG. 17A to generate print data2302, 2303, 2304, and 2305 of each pass. This embodiment is the same asthe first embodiment except that the print ratios of the third andfourth passes are different from those in the first embodiment.

For ink droplets ejected (applied) in the first and second passes, theinfluence of a difference in the amount of ink ejected from each nozzleand the deviation of the landing position of ink in the ejectiondirection is averaged by the effect of the multi-pass printing and thedensity unevenness of a print image is reduced. In addition, since thecontact time of the silver particles in the third and fourth passes ismaintained for a long time, the formation of a metal film by the silverparticles progresses and a metallic gloss is improved. The print ratiosof the fourth pass is set to be lower than that in the first embodiment,but are sufficiently higher than the print ratios of the other passeswith a density unevenness reduction function. Therefore, while a silverparticle film is being formed by the contact between the silverparticles after the ejection of the ink droplets in the third pass ends,the ink droplets are ejected in the fourth pass. As a result, thecontact between the silver particles is further increased by theejection of the ink droplets in the fourth pass and the formation of asilver particle film progresses. Therefore, it is possible to print thesame image as that in the first embodiment. In this embodiment, it isalso possible to print an image with a sufficiently high metallic glossand small density unevenness.

Seventh Embodiment

In a seventh embodiment, the number of passes in multi-pass printing istwo, the print ratio of the first pass is set to a low value, and theprint ratio of the second pass is set to a high value.

FIG. 18A illustrates mask patterns 2401 and 2402 for the first andsecond passes as mask patterns for two passes. A black pixel is theprinting allowance pixel. In the mask pattern 2401 for the first pass,the printing allowance pixels are four pixels among all print pixels (16pixels) and the print ratio is set to a low value of 25.0%. In the maskpattern 2402 for the second pass, the printing allowance pixels are 12pixels and the print ratio is set to a high value of 75.0%.

FIG. 18B illustrates print data 2501 for silver ink obtained bybinarizing a solid image in which ink is ejected to all print pixels. Amasking process is performed for the print data 2501 using the maskpatterns 2401 to 2402 illustrated in FIG. 18A to generate print data2502 and 2503 of each pass.

Parts (a) to (c) of FIG. 19 are diagrams illustrating an aspect in whicha print head ejects silver ink on the basis of the print data of eachpass illustrated in FIG. 18B to form a silver particle film on a printmedium. The parts (a) and (b) of FIG. 19 illustrate a state immediatelybefore the silver ink ejected from the print head in each pass lands ona print medium 2601. Similarly to the first embodiment, the timedifference between the passes is about 300 msec and the time from thelanding of the silver ink on the print medium to the end of infiltrationof a solvent in the ink into the print medium is about several tens ofmilliseconds per droplet.

As illustrated in the part (a) of FIG. 19, a small number of inkdroplets are ejected (applied) in the first pass. Therefore, after theink droplets land on the print medium 2601, the ink droplets do comeinto contact with each other and the infiltration of a solvent in theink into the print medium starts as illustrated in the part (b) of FIG.19. In the stage illustrated in the part (b) of FIG. 19, theinfiltration of the solvent in the ink into the print medium almostends.

As illustrated in the part (b) of FIG. 19, a large number of inkdroplets are ejected in the second pass. Therefore, after these inkdroplets land on the print medium 2601, these ink droplets come intocontact with each other and the infiltration of the solvent in the inkinto the print medium starts as illustrated in the part (c) of FIG. 19.Since a large amount of ink is ejected in the second pass and it takes along time for the solvent to be infiltrated into the print medium or tobe evaporated, the formation of a metal film by the silver particlesprogresses and a silver particle film with a high metallic gloss isformed (part (d) of FIG. 19).

The first pass with a low print ratio has a function of reducing thedensity unevenness of a print image. In addition, the contact betweenthe silver particles occurs by the ejection of ink droplets in thesecond pass with a high print ratio. As a result, the formation of ametal film progresses and an image with a high metallic gloss isprinted. In this embodiment, since the first pass is only the pass witha low print ratio which has the density unevenness reduction function,the effect of reducing density unevenness is less than that in the firstembodiment, but an image with a higher metallic gloss can be printed. Inthis embodiment, it is also possible to print an image with asufficiently high metallic gloss and small density unevenness.

Eighth Embodiment

An eighth embodiment is the same as the first embodiment in that thenumber of passes in multi-pass printing is four, but differs from thefirst embodiment in a method for creating the print data of each pass.Specifically, in the first embodiment, multi-valued print data isbinarized and the print data is distributed on the basis of the printratio of each pass. In contrast, in the eighth embodiment, first,multi-valued data is converted into paired data for each pass on thebasis of the print ratio of each pass and each multi-valued data itemfor each pass is quantized to generate binary print data.

FIG. 20 illustrates multi-valued print data 2701 for silver ink whichcorresponds to a solid image in which ink is ejected to all printpixels. The multi-valued print data 2701 is converted into multi-valueddata 2702, 2703, 2704, and 2705 of each pass on the basis of the printratios (12.5%, 12.5%, 12.5%, and 62.5%) of each pass. These multi-valueddata 2702, 2703, 2704, and 2705 are binarized to generate print data2706, 2707, 2708, and 2709 of each pass. In this embodiment, a knowndither method is used as a binarization method. In addition, differentdither methods are used for each pass such that these print data of eachpass complement each other. The binarization method is not particularlylimited.

A print head ejects silver ink droplets on the basis of the generatedprint data of each pass to apply silver ink to a print medium. Since theprint ratios of each pass are the same as those in the first embodiment,the description thereof will not be repeated. In this embodiment inwhich a print data creation method is different from that in the firstembodiment, it is also possible to print an image with a sufficientlyhigh metallic gloss and small density unevenness.

Ninth Embodiment

A ninth embodiment is the same as the first embodiment in that thenumber of passes is four and the print ratio of the fourth pass is setto a high value. However, in this embodiment, the print ratio of thefourth pass varies depending on a print duty based on print data.

The print duty means the amount of ink ejected (applied) to a unit printarea by one printing scan of the print head. The print duty can becalculated for each type of ink on the basis of print data. For example,the number of dots to be formed in each of a plurality of unit areasforming a print area (the number of pixels to which ink droplets areejected) by one printing scan is counted and the count values for eachunit area are added to calculate the total number of dots (the totalnumber of pixels) to be formed in the print area by one printing scan.Then, the proportion of the total number of dots to the number of dotsthat can be formed in the print area (the number of pixels to which inkdroplets can be ejected) by one printing scan can be calculated as theprint duty.

FIG. 21 is a flowchart illustrating a process which sets a mask patternaccording to the print duty and performs printing.

First, in the print data created by the above-mentioned print datageneration process, the proportion of the pixels to which silver ink isejected (applied) is calculated as an “average duty” (S101). Then, thecalculated average duty is compared with a predetermined threshold value(S102). In a case where the average duty is equal to or greater than thethreshold value, a first mask pattern is set (S103). A masking processis performed for the print data using the first mask pattern and animage is printed on the basis of the processed print data in each pass(S104). On the other hand, in a case where the calculated average dutyis less than the threshold value, a second mask pattern is set (S105). Amasking process is performed for the print data using the second maskpattern and an image is printed on the basis of the processed print datain each pass (S106). As such, the mask pattern is set according to theduty of the print data and printing is performed.

In this embodiment, the mask pattern according to the first embodimentillustrated in FIG. 9A is used as the first mask pattern. In the maskpattern, the print ratios of the first to third passes are set to 12.5%and the print ratio of the fourth pass is set to 62.5%. In addition, themask pattern according to the second embodiment illustrated in FIG. 12Ais used as the second mask pattern. In the mask pattern, the printratios of the first to third passes are set to 6.25% and the print ratioof the fourth pass is set to 81.25%. That is, in the second maskpattern, the print ratios of the first to third passes are lower thanthose in the first mask pattern and the print ratio of the fourth passis higher than that in the first mask pattern. In this embodiment, thethreshold value compared with the average duty is 80.

FIG. 22A illustrates original print data 2901 and print data 2902 havingdifferent print duties. First, a case where an image is printed on thebasis of the print data 2901 will be described.

The CPU calculates the average duty of the received print data 2901(S101 in FIG. 21). Since the print data 2901 corresponds to a solidimage in which ink is ejected to all print pixels, the average duty is100. Then, the average duty is compared with the threshold value (S102).Since the average duty of the print data 2901 is 100 that is greaterthan the threshold value of 80, the first mask pattern is set (S103). Amasking process is performed for the print data 2901 using the firstmask pattern to generate the print data of each pass and an image isprinted on the basis of the print data (S104). Since a method forgenerating the print data of each pass from the print data 2901 usingthe first mask pattern is the same as that in the first embodiment, thedescription thereof will not be repeated.

Since the first mask pattern is used for the print data 2901 with a highprint duty, it is possible to print an image with a sufficiently highmetallic gloss and small density unevenness.

Next, a case where an image is printed on the basis of the print data2902 will be described.

The CPU calculates the average duty of the received print data 2902(S101 in FIG. 21). Since the print data 2902 corresponds to an image inwhich ink is ejected to 12 pixels among all print pixels (16 pixels),the average duty is 75. Then, the average duty is compared with thethreshold value (S102). Since the average duty of the print data 2902 is75 that is less than the threshold value of 80, the second mask patternis set (S105). A masking process is performed for the print data 2902using the second mask pattern to generate the print data of each passand an image is printed on the basis of the print data (S106).

FIG. 22B is a diagram illustrating a process of generating print data3002, 3003, 3004, and 3005 of each pass from the print data 2902 usingthe second mask pattern (the mask pattern illustrated in FIG. 12A).Since the process is the same as that in the first embodiment exceptthat the print ratios of each pass are different from those in the firstembodiment, the description thereof configuration will not be repeated.

For ink droplets ejected (supplied) in the first to third passes with alow print ratio, the influence of a difference in the amount of inkejected from each nozzle and the deviation of the landing position ofink in the ejection direction is averaged by the effect of themulti-pass printing and the density unevenness of a print image isreduced. In addition, since the contact time of the silver particles inthe fourth pass with a high print ratio is maintained for a long time,the formation of a metal film by the silver particles progresses and ametallic gloss is improved.

In this embodiment, in a case where the duty of the original print datais less than the threshold value (NO in S102), the mask pattern in whichthe print ratio of the fourth pass that is higher than that in a casewhere the duty is equal to or greater than the threshold value (YES inS102) is selected and used (S105). Therefore, the amount of silver inkejected in the fourth pass with a high print ratio is equal to orgreater than a predetermined value, regardless of the duty of the printdata. As a result, it is possible to print an image with a high metallicgloss and small density unevenness.

According to this embodiment, it is possible to print an image with asufficiently high metallic gloss and small density unevenness,regardless of the print duty of the original print data.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2017-136434, filed Jul. 12, 2017, which is hereby incorporated byreference wherein in its entirety.

What is claimed is:
 1. A printing apparatus comprising: a print unitconfigured to apply metallic printing material to a print medium, themetallic printing material including a metallic compound for imparting ametallic gloss on the print medium; and a control unit configured toperform a plurality of printing scans to the same area of a print mediumto print an image on the print medium, so that in a printing scan, themetallic printing material is applied from the print unit to the printmedium while relatively moving the print unit and the print medium,wherein the control unit is further configured to set, when performingthree or more times of scans to the same area of a print medium, a printratio of the metallic printing material in a predetermined scan to beequal to or greater than 31.25% of a sum of print ratios of the metallicprinting material in the plurality of printing scans.
 2. The printingapparatus according to claim 1, wherein the control unit sets, whenperforming three or more times of scans to the same area of a printmedium, a print ratio of the metallic printing material in apredetermined scan to be equal to or greater than 62.5% of a sum ofprint ratios of the metallic printing material in the three or moretimes of scans.
 3. The printing apparatus according to claim 1, whereinthe control unit sets any one of the printing scans corresponding to alatter half of the three or more scans as the predetermined scan.
 4. Theprinting apparatus according to claim 1, wherein the control unit setstwo or more consecutive printing scans as the predetermined scan.
 5. Theprinting apparatus according to claim 1, wherein the control unitchanges the print ratio of the predetermined scan depending on an amountof metallic printing material applied by the three or more times ofscans.
 6. The printing apparatus according to claim 1, wherein thecontrol unit sets the print ratio of the predetermined scan such thatthe print ratio of the predetermined scan becomes higher as an amount ofmetallic printing material applied by the three or more times of scansbecomes smaller.
 7. The printing apparatus according to claim 1, whereinthe control unit sets a print ratio of the metallic printing material inat least one scan of the three or more times of scans different from thepredetermined scan to be greater than zero.
 8. The printing apparatusaccording to claim 1, wherein the print ratio of the metallic printingmaterial in a predetermined scan is equal to or greater than half a sumof print ratios of the metallic printing material in the three or moretimes of scans.
 9. The printing apparatus according to claim 1, whereinthe print ratio of the metallic printing material in each of the threeor more times of scans is determined by dividing a unit area on theprint medium by an area covered by dots to be formed in the unit area.10. The printing apparatus according to claim 1, wherein the metallicprinting material is metallic ink and the print unit is print headincluding a plurality of ejection ports for ejecting metallic ink to aprint medium, and wherein the print head ejects the metallic ink to theprint medium while the print head scans over the print medium.
 11. Theprinting apparatus according to claim 1, wherein the metallic printingmaterial imparts silver color on the print medium.
 12. A printingapparatus comprising: a print unit configured to apply metallic printingmaterial to a print medium, the metallic printing material including ametallic compound for imparting a metallic gloss; and a relativemovement unit configured to perform a relative movement between a printmedium and a print head, wherein the print unit prints an image on theprint medium while the relative movement unit performs the relativemovement, and wherein when printing an image with three or more times ofthe relative movements to the same area of a print medium, the printunit applies the metallic printing material to be equal to or greaterthan 31.25% of a total amount of the metallic printing material appliedto the same area print ratios of the metallic printing material within apredetermined movement.
 13. The printing apparatus according to claim12, wherein the metallic printing material is metallic ink and the printunit is print head including a plurality of ejection ports for ejectingmetallic ink to a print medium, and wherein the print head ejects themetallic ink to the print medium while the print head scans over theprint medium.
 14. The printing apparatus according to claim 12, whereinthe metallic printing material imparts silver color on the print medium.15. The printing apparatus according to claim 14, wherein when printingan image with three or more times of the relative movements to the samearea of a print medium, the print unit applies the metallic printingmaterial to be equal to or greater than 62.5% of a total amount of themetallic printing material applied to the same area print ratios of themetallic printing material within a predetermined movement.
 16. Aprinting apparatus comprising: a print unit configured to apply metallicprinting material to a print medium, the metallic printing materialincluding a metallic compound for imparting a metallic gloss on theprint medium; and a control unit configured to perform a plurality ofprinting scans to the same area of a print medium to print an image onthe print medium, so that in a printing scan, the metallic printingmaterial is applied from the print unit to the print medium whilerelatively moving the print unit and the print medium, wherein thecontrol unit sets a print ratio of the metallic printing material in apredetermined scan to be equal to or greater than 62.5% of a sum ofprint ratios of the metallic printing material in the plurality ofprinting scans, and sets a print ratio of the metallic printing materialin at least one scan of the plurality of printing scans different fromthe predetermined scan to be greater than zero.
 17. The printingapparatus according to claim 16, wherein the metallic printing materialis metallic ink and the print unit is print head including a pluralityof ejection ports for ejecting metallic ink to a print medium, andwherein the print head ejects the metallic ink to the print medium whilethe print head scans over the print medium.
 18. The printing apparatusaccording to claim 16, wherein the metallic printing material impartssilver color on the print medium.
 19. A printing apparatus comprising: aprint unit configured to apply metallic printing material to a printmedium, the metallic printing material including a metallic compound forimparting a metallic gloss; and a relative movement unit configured toperform a relative movement between a print medium and a print head,wherein the print unit prints an image on the print medium while therelative movement unit performs the relative movement, and wherein theprint unit applies the metallic printing material to be equal to orgreater than 62.5% of a total amount of the metallic printing materialapplied to the same area in a predetermined relative movement of aplurality of the relative movements between the print medium and theprint head and applies the metallic printing material in at least onerelative movement between the print medium and the print head differentfrom the predetermined relative movement to be greater than zero. 20.The printing apparatus according to claim 19, wherein the metallicprinting material is metallic ink and the print unit is print headincluding a plurality of ejection ports for ejecting metallic ink to aprint medium, and wherein the print head ejects the metallic ink to theprint medium while the print head scans over the print medium.
 21. Aprinting method comprising: printing to apply metallic printing materialto a print medium, the metallic printing material including a metalliccompound for imparting a metallic gloss on the print medium; andcontrolling to perform a plurality of printing scans to the same area ofa print medium to print an image on the print medium, so that in aprinting scan, the metallic printing material is applied from a printunit to the print medium while relatively moving the print unit and theprint medium, wherein the controlling is performed to set, whenperforming three or more times of scans to the same area of a printmedium, a print ratio of the metallic printing material in apredetermined scan to be equal to or greater than 31.25% of a sum ofprint ratios of the metallic printing material in the plurality ofprinting scans.